Current and previous methods of determining a precise location of a vehicle when underwater on a ships' hull or the vehicle's direction of travel on the hull are based on acoustic or sonar systems. These systems transmit hi-frequency sound waves through the water and register the vibrations reflected back from the desired object. Positioning is then determined by sonar triangulation, a surveying method that provides coordinates of where the desired object is in reference to a “baseline station” which acts as a marker or reference point for navigation. A basic system would consist of fixed and mobile transponders/beacons and a computer with a software program that determines the relative position of the mobile transponder(s) in relation to the fixed one.
There are several disadvantages associated with these types of systems. First, they use active high powered systems that transmit sound waves underwater, which is not desired. Additionally, these systems are expensive and high maintenance. For example, in order to work properly these systems require continual re-deployment and calibration of the beacons. Also, a large learning curve for the operators is also required.